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I was always taught that twin and earth cables should be used in domestic only and singles/multicore in commercial?
Why is that ? I mean there isn't anything wrong with using 1.5mm2 twin and earth with 1.0mm2 CPC for lighting circuits.
Regards,
J
AJJewsbury:
There is a potential issue about the prospective fault currents and reduced c.p.c. (especially where MCBs are used as the energy-let though tends to increases with increasing fault current) - as some larger commercial and industrial premises tend to have beefier supplies and hence higher fault currents.
Using generic data (e.g. from BS EN 60898) you'd have a hard time proving that a 1.0mm2 c.p.c. was good above 3kA.
- Andy.
Using generic data from BS EN 60898, you'd have a job anyway, because only the maximum at the rated short-circuit capacity is provided, i.e. if you have a 6 kA breakers (as in most domestic CUs), the lowest let-through energy quoted is 35000 ampere-squared seconds.
This doesn't even permit 1.5 sq mm copper conductors (of live conductors, or cpc) for fault (that is, short-circuit) protection!
AJJewsbury:
There is a potential issue about the prospective fault currents and reduced c.p.c. (especially where MCBs are used as the energy-let though tends to increases with increasing fault current) - as some larger commercial and industrial premises tend to have beefier supplies and hence higher fault currents.
Using generic data (e.g. from BS EN 60898) you'd have a hard time proving that a 1.0mm2 c.p.c. was good above 3kA.
- Andy.
Using generic data from BS EN 60898, you'd have a job anyway, because only the maximum at the rated short-circuit capacity is provided, i.e. if you have a 6 kA breakers (as in most domestic CUs), the lowest let-through energy quoted is 35000 ampere-squared seconds.
This doesn't even permit 1.5 sq mm copper conductors (of live conductors, or cpc) for fault (that is, short-circuit) protection!
